Radiological imaging device, method and program of control associated with the device

ABSTRACT

Radiological imaging device comprising an emitter of an X-ray beam and a receiver of the X-ray beam after it has crossed an organ, the organ being capable of being placed between the receiver and a compression element, capable of being removably fixed on the device. A calculation unit includes a means for optimizing the image quality over a particular area defined by the compression element.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This applications claims the benefit of a priority under 35 USC119 to French Patent Application No. 0005311 filed Apr. 26, 2000, theentire subject matter contents which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

[0002] The present invention belongs to the field of radiology intendedfor study of object in particular of the human body in general and ofcertain organs in particular, such as the breasts, the heart, thecirculatory system, etc.

[0003] As is standard, a radiology device comprises an X-ray tubecapable of emitting an X-ray beam along a given axis, an X-ray receiverplaced on the path of the X-ray beam, the organ to be studied beinginterposed between the X-ray tube and the receiver, and a support of theX-ray tube and receiver capable of displacing them along at least oneaxis, with a view to obtaining the positioning desired in relation tothe organ to be studied. The radiology device further contains anelectric power supply intended for the X-ray tube and possibly differentelectric motor or actuators, and a control of the X-ray tube making itpossible to obtain the proper adjustments. The X-ray receiver isequipped with a digital type X-ray detector to display the imageobtained on a video screen and/or to print it. U.S. Pat. No. 5,539,797is an example of a known device.

[0004] When used the operator could commit errors resulting in seriousdisadvantages. For example, in the case of mammography, a lateral errorcan lead to taking a biopsy not on the breast presentingmicrocalcifications or other symptoms, but on the other breast with noneof these symptoms.

BRIEF DESCRIPTION OF THE INVENTION

[0005] The present invention seeks to reduce the possibility ofradiography errors.

[0006] The present invention seeks to automate the marking of an X-ray.

[0007] The present invention seeks to improve the quality of the imagesobtained.

[0008] The radiological imaging device, according to one aspect of theinvention comprises means for emission of an X-ray beam and means forreceiving the X-ray beam, after it has crossed an organ to be studied,and means for calculating capable of controlling the means for emissionand processing data coming from the means for receiving, the organ beingcapable of being placed between the means for receiving and an elementcompressing the organ. The means for calculating comprises a means foroptimizing the image quality on a particular area defined by thecompression element.

[0009] The radiological imaging device, according to another aspect ofthe invention, is of the type comprises means for emission of an X-raybeam, means for receiving the X-ray beam after it has crossed an organto be studied, an element presenting a given X-ray absorption capable ofbeing removably fixed on the device, and a means for calculation forcontrolling the means for emission and of processing data from the meansfor receiving. The means for calculation include a means for optimizingthe image quality over a particular area defined by the element.

[0010] The radiological imaging process, according to one aspect of theinvention, includes the following stepes:

[0011] (a) an organ compression element is mounted on a radiologicaldevice, of the type including means for emission of an X-ray beam, meansfor receiving the X-ray beam after it has crossed an organ to be studiedand means for calculating capable of controlling the means for emissionand processing data coming from means for the receiving;

[0012] (b) the organ is placed between the means for receiving and thecompression element, and a first radiological image is taken; and

[0013] (c) the first radiological image is processed in order tooptimize the image quality over a particular area defined by thecompression element.

[0014] The radiological imaging process, according to another aspect ofthe invention, comprises the following steps:

[0015] (a) an element presenting a given X-ray absorption is placed onthe path of an X-ray beam of a radiological device, the radiologicaldevice being of the type including means for emission of an X-ray beam,means for receiving the X-ray beam after it has crossed an organ to bestudied and means for calculation capable of controlling the means foremission and processing data from the means for receiving;

[0016] (b) the organ is placed on the path of the X-ray beam, a firstradiological image is taken, and

[0017] (c) the first radiological image is processed in order tooptimize the image quality on a particular area defined by the element.

[0018] The control program, according to one aspect of the invention,includes program code means for using the stage of the above-mentionedprocess.

[0019] The support, according to one aspect of the invention, is capableof being read by a device reading the program code means which arestored there and are suitable for use of the stages of theabove-mentioned process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] An embodiment of the invention is illustrated by:

[0021]FIG. 1 is a view in perspective of a radiology device;

[0022]FIG. 2 is a partial side view showing the cooperation of acompression element and a radiology device;

[0023]FIG. 3 is a schematic view of means for recognition; and

[0024]FIG. 4 is a diagrams of the steps of the process;

[0025]FIG. 5 is a flow chart of a method of use of the process;

[0026]FIG. 6 is a curve showing the limited histogram in relation to thereal histogram;

[0027]FIG. 7 is a curve showing a way of choosing WL; and

[0028]FIG. 8 is a diagram of the stages of the process of obtaining aninvariant contrast.

DETAILED DESCRIPTION OF THE INVENTION

[0029] The invention is applicable in the medical field and, inparticular, to an X-ray imaging device.

[0030] The device may include a means for recognition of the compressionelement.

[0031] The means for recognition may include at least one detectionelement and an adapter connected to an output of the detection elementto transfer data from the detection element to a communication busassociated with the device. The detection element and the adapter can beformed on the same circuit, for example, integrated. The detectionelement can be of a mechanical type, such as a switch or magnetic, forexample, a relay sensitive to magnetism or optical, for example, aphotosensitive cell, etc.

[0032] In one embodiment of the invention, the means for calculation iscapable of processing data from the means for recognition.

[0033] The device includes a coupling part of a compression element andthe means for recognition may be placed in the coupling part.

[0034] The means for emission and the means for reception can besupported by an arm pivoting on at least one axis supported by a frame.The device can include a means for detecting the angle of pivoting ofthe arm, a means for entering data relating to the organ to be studied,a processing means capable of determining the type of image which isgoing to be taken as a function of the angle of pivoting and of the datarelating to the organ, and a means for displaying on the image the typeof image determined by the processing means or for storing the type ofimage determined with the image data, for example, in the heading of acomputer file. The means for receiving may be capable of transformingthe X-ray beam into a digital electronic signal.

[0035] The device can contain a means for recognition of the compressionelement.

[0036] The compression element preferably includes a coder capable ofcooperating with the means for recognition. The number of data that thecoder can code will be equal to the number of data that the means forrecognition can decode.

[0037] The compression element, according to one aspect of theinvention, is capable of being removably fixed on a radiological imagingdevice, of the type including means for emission of an X-ray beam andmeans for receiving the X-ray beam after it has crossed an organ to bestudied. The organ is capable of being placed between the means forreceiving and the organ compression element. The compression elementincludes a coder capable of cooperating with a compression element meansfor recognition provided on a radiological imaging device.

[0038] The coder will be of the same type as the detection element:based on protuberances or hollows if the detection element is ofmechanical type, based on magnets if the detection element is ofmagnetic type, based on light or dark surfaces if the detection elementis of optical type, etc.

[0039] The compression element preferably includes a coupling part on aradiological imaging device, and the coder is integral with the couplingpart.

[0040] The particular area is defined by the surface of the compressionelement in contact with the organ to be studied.

[0041] In one embodiment of the invention, optimization of the imagequality is carried out from a histogram of the X-rayed image (realhistogram), from a mathematical model of the image chain and from theobject obtained by calibration.

[0042] (a) The mathematical model of the image chain and object and aset of parameters of acquisition, of the detector, of the positioner andof the object can be used to determine two gray level values, min grayand max_gray, taken in the particular area and delimiting a useful graylevel area,

[0043] (b) The part below min gray and the part above max_gray can beeliminated in the real histogram in order to obtain a limited histogram,

[0044] (c) A set of rules can be applied to the limited histogram inorder to determine a WL brightness level,

[0045] (d) A WW contrast can be obtained from the WL brightness leveland possibly from one or more parameters chosen by the user or fixed apriori.

[0046] The (μmin) minimum linear attenuation coefficient of the objectcan be estimated from known values of the linear attenuation coefficientof the least attenuating tissues of the object (adipose tissues for thebreast) for the energies of the X-ray spectrum determined by theacquisition parameters and makes it possible, with the parameter of thedetector, the parameters of the positioner, the acquisition parametersand the parameters of the object, through a mathematical model of theimage chain and object, to determine min-gray.

[0047] The (μmax) maximum linear attenuation coefficient of the objectcan be estimated from known values of the linear attenuation coefficientof the most attenuating tissues of the object (fibrous tissues for thebreast) for the energies of the X-ray spectrum determined by theacquisition parameters or, more precisely, from the mechanical thicknessof the compressed breast, the acquisition parameters, the mathematicalmodel of the image chain and the object and a quantity of photonsobtained as a result of a pre-exposure made on an area of maximumdensity of the object, and makes it possible, with the parameters of thedetector, the parameters of the positioner, the acquisition parametersand the object parameters, through a mathematical model of the imagechain and object, to determine the min_gray gray level.

[0048] The limitation of the histogram can introduce two gray levels(min_gray and max_gray) encompassing an area of gray levels in which theWL brightness is determined.

[0049] A match can be made between the limited histogram and amathematical model of the histogram in order to determine the value of aradiological thickness characterizing the object.

[0050] Matching between the limited histogram and mathematical model ofthe histogram can be carried out by applying a method of minimization oferrors between two functions.

[0051] For the acquisition of a digital radiographic image of an object,an acquisition chain can contain a stage of equalization of theexponential attenuation effect of radiation by using a modifiedlogarithmic function, so that the perception of contrast of a givendifference in thickness remains invariant regardless of the means ofacquisition.

[0052] The brightness level and the contrast obtained from a mediumattenuation coefficient of the image independent of the brightness levelcan act on a stage of visualization so that the signals coming out ofthe equalization stage (space of radiological thicknesses) aredimensioned in the space of real thicknesses.

[0053] More precisely, the control program can be designed for acalculation unit of a radiological imaging device of the type comprisingan emitter of an X-ray beam, a receiver of the X-ray beam after it hascrossed an organ to be studied, and a calculation unit capable ofcontrolling the emitter and processing data from the receiver. The organis capable of being placed between the receiver and an organ compressionelement. The compression element is capable of being removably fastenedon the device. The program includes a module for processing of the datafrom the recognition unit in order to optimize the image quality on aparticular zone defined by the compression element.

[0054] As can be seen in FIG. 1, the radiology apparatus comprises anX-ray tube 1 as a means for emission of an X-ray beam centered on anaxis 2. On the path along which the X-rays are propagated and centeredon axis 2, a receiver 3 is placed, as a means for receiving andtransforming the incident X-rays into an electronic signal. The receiver3 can be equipped with an X-ray detector of solid state type. The tube 1and the receiver 3 are each supported at an opposite end of an arm 4supported by a frame, not represented. The tube 1 and receiver 3 aremounted in rotating relation to the frame on an axis 5 perpendicular tothe plane of the figure and passing through the intersection of axis 2and the axis referenced 6, those three axes being perpendicular to eachother. The arm 4, the tube 1 and the receiver 3 can be rotated on onecomplete turn in relation to the frame. The X-ray detector of thereceiver 3 is equipped with a scanning system for reading the matrix ofelementary detection cells constituting the detector.

[0055] In FIG. 1, a radiology apparatus with one axis is represented. Ofcourse, this invention also applies to multiple-axis radiologyapparatuses, for example, with C-arms with three axes or four axes.

[0056] The invention can be applied to a mammography apparatus using ascreen-film pair (inside a cassette) as well as an apparatus using adigital detector. In the case of a film detector, the view nameinformation will then be optically written on the film.

[0057] The use of compression ball or element information for control ofexposure time as a function of the signal received on a pre-exposure isentirely possible. It is then necessary for the mammography apparatus touse a system composed of several cells (a cell matrix, for example) tomeasure the quantity of X-rays reaching different places of the detectorduring pre-exposure. The cell located under the compression ball andcorresponding to the radiologically densest area of the object studiedis typically chosen. A combination of the signal coming from severalcells is also possible according to the average, the median value, etc.The method previously described chooses the maximum as algorithm.

[0058] In FIG. 2, a slightly different embodiment is illustrated, inwhich the column 8 of the radiology device 1 contains a horizontal slide19 formed by a groove 20 limited by an upper edge 21 and a lower edge22, so that the bottom 23 of the groove 20 presents a greater heightthan its opening 24.

[0059] A compression element or ball 25 is capable of cooperating withthe slide 19 and contains a coupling part 26, a link part 27 and acontact part 28. The coupling part 26 is of a shape conforming to theslide 19 so that it can be placed inside. The coupling part 26 presentsa rectangular section completed by two protuberances, upper 29 and lower30, designed to be accommodated in the bottom 23 of the groove 20. Thedistance between the opposite ends of the protuberances 29 and 30 isgreater than the distance between the opposite ends of the upper edge 21and lower edge 22. The link part 27 extends from the coupling part 26 tothe outlet of the groove 20 and supports the contact part 28, whichpresents a flat lower surface 31 capable of coming in contact with anorgan, for example, the breast of a patient benefiting from amammography examination. The contact part 28 can be made of materialwith low X-ray absorption, such as the material having the trade namePlexiglas, for example.

[0060] The compression element 25 can glide horizontally in the slide 19and is removable from the column 8. For one and the same radiologydevice, different compression elements are generally used, of which onlythe coupling part 26 is similar for coupling in the slide 19. A means,not represented, for locking the translation movement in the slide 19can be provided. To recognize the different compression elements, acoder 32 is fastened in or on the coupling part 26 of each compressionelement normally intended to be used with a corresponding radiologydevice. The coder can be of mechanical type in the form of keys, opticalin the form of light or dark areas, or magnetic in the form of magnets.Here, the coder 32 contains a plurality of magnets, for example, four orfive, cropping out of the surface of the coupling part 26 on the side ofthe bottom 23 of the groove 19.

[0061] The column 8 of the radiology device is equipped with a detectionelement 33 of the same technology as the coder. Here, the detectionelement 33 is capable of detecting a magnetic field emitted by the coder32 and can contain a plurality of Hall-effect sensors or “reed” typemagnetic relays in equal number to the number of magnets of the coder32.

[0062] The radiology device 1 can be equipped with a detection unit 34,as illustrated in FIG. 3. The detection unit 34 contains four relays 35belonging to a detection element 33. Each relay 35 is fed through a line36 with weak low-voltage electric power.

[0063] An adapter 37 receives a signal from a relay 35 and renders thesignal compatible, notably, in voltage and output impedance, with thestandard used for the electronics of the radiology device 1, forexample, HCMOS. The adapters 37 can be separate or grouped, for example,on an integrated circuit.

[0064] The detection unit 34 further contains a serial converter 38 topermit communication by means of a data transfer bus 39, for example, RS232, to a means for calculation unit 40 belonging to the radiologydevice 1. The calculation unit 40 may carry out image processing andwill be equipped with memory and software for that purpose.

[0065] The radiology device 1 can be operated as illustrated by FIG. 4.In stage 41, the radiology device 1 detects the type of compressionelement 25 placed in the slide 19 of the column 8, detection beingcarried out by the detection unit 34. In stage 42, the calculation unit40 receives the “compression_element_type” information from thedetection unit 34. In stage 43, the calculation unit 40 sends the“compression_element_type” information to a matching table stored inmemory and receives from the table, in stage 44,“useful_surface_coordinates” information relating to the surface forwhich it is of interest to optimize the image quality. That surface canbe the flat lower surface 31 of the contact part 28 of the compressionelement 25. In stage 45, the calculation unit 40 sends a command to theX-ray source 7 and, in particular, to a collimator, not represented,forming part of the source 7, to adjust the X-ray beam to the usefulsurface; in other words, for the area of the organ exposed to X-rays tomatch the useful surface, in order to reduce the total X-ray dosereceived by the patient.

[0066] The optimization can be achieved as follows: application of theprocess to the automatic determination of WL brightness and WW contrastis described in the particular case of mammography.

[0067] The first stage uses a mathematical model 46 of the image chainand of the object with the following parameters in input data:

[0068] (a) thickness of the compressed breast and parameters of thepositioner (incidence of filming, enlargement factor, particular areadefined by the compression element used, thickness of the object,compression force, etc.) as parameters 47 of the positioner,

[0069] (b) parameters 48 of the detector (ratio between the X-ray flowreceived on the detector and the gray levels of the image produced,etc.),

[0070] (c) acquisition parameters 49 (track, filter, kV, mAs, etc.),

[0071] (d) object parameters (mechanical thickness of the breast, μminminimum and μmax maximum values of the linear attenuation coefficient ofthe object, etc.).

[0072] The breast consisting mainly of fibrous and adipose tissues, ifthere is no information on the composition of the breast, μmin and μmaxcan be estimated by making two extreme suppositions:

[0073] μmin corresponds to the linear attenuation coefficient of theleast attenuating tissues of the object (adipose tissues for the breast)inside the particular area defined by the compression element for theenergies of the X-ray spectrum determined by the acquisition parameters;

[0074] μmax can be estimated in two ways: on the one hand, like μmin, byconsidering that μmax corresponds to the linear attenuation coefficientof the most absorbent tissues of the object (fibers for the breast)inside the particular area defined by the compression element for theenergies of the X-ray spectrum determined by the acquisition parameters.In another more precise way, from a mathematical model of the imagechain, the mechanical thickness of the compressed breast, theacquisition parameters and a quantity of photons following apre-exposure made on an area of maximum density (which makes it possibleto estimate the value of the linear attenuation coefficientcorresponding to the most attenuating area of the object).

[0075] The set of parameters introduced in the mathematical model 46 ofthe image chain and of the object makes it possible to have two graylevel values on output: min_gray and max_gray (FIG. 6). Those twovalues, in fact, delimit the useful area, which is an area of graylevels really pertaining to the breast. In fact, thanks to the twoextreme values of the composition of the breast, μmin and μmax, an areadelimited by two extreme values, min_gray and max_gray, was obtained,outside of which the gray levels do not correspond to the breast. Moreprecisely, the part of the gray levels below min_gray corresponds toobjects more attenuating than the object of interest, and the part ofthe gray levels above max_gray corresponds to the bottom of the image.Inside the particular area defined by the compression element, theuseful area is determined. That stage 51 is a segmentation stage, for itmakes it possible to delimit the useful area.

[0076] A match is then made (stage 54) between the two min_gray andmax_gray values and a histogram 53 taken from the radiographic image 52of the breast (real histogram). More precisely, the part below min_grayand the part above max_gray are eliminated so that the useful area isalone preserved in order to obtain a limited histogram 55 (FIG. 6).

[0077] The WL brightness is a value included in the useful area and canbe obtained in several ways. One way of obtaining the WL brightness isapplication of a set of pre-established rules 56 to the limitedhistogram 55. A set of rules 56 can include:

[0078] (a) determination of the gray level corresponding to the maximumof the limited histogram;

[0079] (b) conservation of an x % quantity (typically 95%) of theoccurrences of the histogram limited to the right of the maximum andalso x % of the occurrences to the left of the maximum: a reconstructedhistogram is thus obtained;

[0080] (c) determination of the WL brightness as median value of thereconstructed histogram (FIG. 7).

[0081] It is also possible to obtain the WL brightness with betterprecision by having the set of rules stage preceded by a matching stage57. That stage introduces a mathematical model 58 of the histogram inwhich:

[0082] (a) the shape of the breast is a cylinder generated by rotationon an axis, from a rectangle, one of the narrow sides of which is closedby a semicircle of diameter equal to the length of that narrow side;

[0083] (b) the composition of the breast is homogeneous, for example,100% fat;

[0084] (c) a histogram is established, which corresponds to probabilityas a function of the radiological thickness of the breast;

[0085] (d) the maximum of the histogram obtained represents the maximumthickness of the breast which, multiplied by the attenuationcoefficient, gives the maximum radiological thickness corresponding tothe adipose tissue.

[0086] Matching of the two histograms (mathematical model 58 and limitedhistogram 55) makes it possible to determine on the limited histogram 55the value of the maximum radiological thickness corresponding to theadipose tissue in the breast.

[0087] This therefore makes it possible to determine the radiologicalthickness values of the different components of the breast.

[0088] This matching is made by employing a method of minimization oferrors between two functions like, for example, the least squaresmethod.

[0089] An adequate set of rules can then be applied to determine the WLbrightness. For example, WL=α.E with E representing the radiologicalthickness value obtained from the mathematical model 58 of thehistogram.

[0090] The following step corresponds to determination of the WWcontrast by using the WL brightness. The WW contrast is obtained from afunction introducing the WL brightness and possibly from otherparameters, notably, a parameter G (FIG. 7), which is chosen by theuser. The parameter G therefore renders this process adaptable to eachuser: WW=g(WL, G), g being a function which, from WL brightness and G,determines the WW contrast that therefore represents a gray level scalearound WL brightness.

[0091] It is also possible to determine the WW contrast independent ofthe WL brightness.

[0092] First, μ medium is determined from the information drawn from thelimited histogram. For example, one can take the μ corresponding to themedian value of the limited histogram as μmedium.

[0093] A law introducing a constant Cte is then used to deduce from itthe WW contrast:

WW=Cteμ(spectrum)

[0094] That ratio is true in a monoenergetic case, but in general the WWcontrast is a function of the spectrum.

WW=f(spectrum)

[0095] The self-contrast operation is thus carried out, since the WLbrightness and WW contrast are established.

[0096] What is now going to be described is the way in which theperception of contrast of a difference in thickness remains invariant,regardless of the means of acquisition and the objects, in accordancewith FIG. 8.

[0097] The use of X-rays with the object entails an exponentialattenuation of intensity I in the image:

I=loexp(−∫μdl)

[0098] Io is a constant, dl represents an infinitesimal quantitycorresponding to the distance along the path connecting the focus of theX-ray and the detector.

[0099] ∫dl represents the radiological thickness for a given area of anobject.

[0100] In order to obtain that value, a pre-LUT (look-up table)operation is performed, making it possible to equalize the exponentialattenuation by using a modified logarithmic function. It is the to bemodified, for the lowest gray levels are transformed according to alinear function, while the logarithmic function progressively intervenesfor the other gray levels.

[0101] One is thus in the space of radiological thicknesses in which aradiological thickness is noted μH with H the real thickness.

[0102] It is intended, finally, to make a change of space in order to bein the space of real thicknesses.

[0103] Self-contrast supplies us with the values of WW contrast and WLbrightness that are introduced in a display LUT. The display LUT makesit possible to eliminate μ. In the case of a monoenergetic image, thatoperation comes down to a division by μ. This operation is possible, forthe WW contrast is proportional to μ.

[0104] The result thus obtained can be introduced in the display systemin order to display the image (FIG. 8).

[0105] The invention makes it possible, among other things, to improvethe quality of the images displayed by a user, while reducing the X-raydose.

[0106] The area on which the exposure is estimated from a pre-exposurecan also be searched. It is then a question of determining, with apre-exposure image obtained with a very low X-ray dose, what is thedensest area of the part of the breast of interest to us in order toestimate the exposure time. Without a priori knowledge of thecompression element used, the search of that area is carried out overthe entire surface of the image. With a priori knowledge of thecompression element used, and knowing the mechanical thickness ofcompression and the geometric enlargement factor used, a search area canbe deduced therefrom on the pre-exposure image, limited to the usefulpart of the compression element used. This is particularly of interestfor compression elements whose compression area is less than thesensitive surface area of the detector.

[0107] A possible optimization of exposure is thus avoided on an areaoutside the particular area defined by the compression element, whichwould have the effect of degrading exposure of the part of the breastunder compression, which is the part of interest to the radiologist. Therisk of an inadequate optimization is thus reduced.

[0108] Knowledge of the compression ball or element used makes itpossible to control the X-ray collimator located at the outlet of theX-ray tube, for the purpose of limiting the irradiated area of theobject studied.

[0109] When a compression ball or element of small surface is used, thecollimator is adjusted, so that the X-rays can cross it, but also sothat the X-rays cannot reach the parts of the object under compressionwhose entry surface would be outside the compression ball. Collimationcan be chosen as a function of the shape or size of the compressionball, according to the size of the ball±N cm in each dimension, thetable unequivocally connecting the compression ball used and thecollimator opening, etc.

[0110] Various modifications in structure and/or steps and/or functionmay be made by one skilled in the art without departing from the scopeof the invention.

What is claimed is:
 1. A radiological imaging device, comprising meansfor emission of an X-ray beam, a means for receiving the X-ray beamafter it has crossed an object to be studied, and means for calculationfor controlling the means for emission and for processing data from themeans for receiving, the object being capable of being placed betweenthe means for receiving and a compression element, the compressionelement being capable of being removably fixed on the device, the meansfor calculation unit a means for optimizing the image quality over aparticular area defined by the compression element.
 2. The deviceaccording to claim 1 , comprising a means for unit of recognition of thecompression element.
 3. The device according to claim 2 , wherein themeans for recognition unit includes at least one detection element andan adapter connected to an output of the detection element for thetransfer of data from the detection element to a communication busassociated with to the device, the means for calculation unit forprocessing data from the means for recognition unit.
 4. A radiologicalimaging device means for emission of an X-ray beam, a means forreceiving the X-ray beam after it has crossed an object to be studied,an element presenting a given X-ray absorption capable of beingremovably fixed on the device, and a means for calculation forcontrolling the means for emission and for processing data from themeans for receiving, the means for calculation including a means foroptimizing the image quality over a particular area defined by theelement.
 5. The device according to claim 4 , wherein the compressionelement includes a coder capable of cooperating with a the means forrecognition of the compression element.
 6. A radiological imagingmethod, in which an object compression element is mounted on aradiological device having means for emission of an X-ray beam, a meansfor receiving of the X-ray beam after it has crossed the object to bestudied and means for calculation unit for controlling the means foremission and for processing data from the means for receiving,comprising the steps of: placing the object between the means forreceiving and the compression element, taking a first radiological, andprocessing the first radiological image is in order to optimize theimage quality over a particular area defined by the compression element.7. The method according to claim 6 , in which the particular area isdefined by the surface of the compression element in contact with theobject to be studied.
 8. The method according to claim 6 , in which,from a histogram of the X-rayed image (real histogram), from amathematical model of the image chain and from the object obtained bycalibration. a) the mathematical model of the image chain and object anda set of parameters of acquisition, of the detector, of the positionerand of the object is used to determine two gray level values, min_grayand max_gray, taken in the particular area and delimiting a useful graylevel area; b) the part below min_gray and the part above max_gray iseliminated in the real histogram in order to obtain a limited histogram;c) a set of rules is applied to the limited histogram in order todetermine a WL brightness level; and d) a WW contrast is obtained fromthe WL brightness level and possibly from one or more parameters chosenby the user or fixed a priori.
 9. The method according to claim 7 , inwhich, from a histogram of the X-rayed image (real histogram), from amathematical model of the image chain and from the object obtained bycalibration. a) the mathematical model of the image chain and object anda set of parameters of acquisition, of the detector, of the positionerand of the object is used to determine two gray level values, min_grayand max_gray, taken in the particular area and delimiting a useful graylevel area; b) the part below min_gray and the part above max_gray iseliminated in the real histogram in order to obtain a limited histogram;c) a set of rules is applied to the limited histogram in order todetermine a WL brightness level; and d) a WW contrast is obtained fromthe WL brightness level and possibly from one or more parameters chosenby the user or fixed a priori.
 10. A radiological imaging process, inwhich an element presenting a given X-ray absorption is placed on thepath of an X-ray beam of a radiological device, the radiological devicecomprising means for emission of an X-ray beam, a means for receivingthe X-ray beam after it has crossed an object to be studied and a meansfor calculation unit for controlling the means for emission and forprocessing data from the means for receiving, comprising the steps of:placing object on the path of the X-ray beam, taking a firstradiological image, and processing the first radiological image in orderto optimize the image quality on a particular area defined by theelement.
 11. Computer program including program code means for using thesteps of the process according to claim 7 .
 12. A computer programincluding program codes for carrying out the steps of the processaccording to claim 8 .
 13. A computer program including program codesfor carrying out the steps of the process of claim 9 .
 14. Supportcapable of being read by a reading device of program code means whichare stored there and are suitable for use of the steps of the processaccording to claim 7 .
 15. Support capable of being ready by a readingdevice of a program code which is stored therein and suitable forcarrying out the steps of claim 8 .
 16. Support capable of being readyby a reading device of a program code which is stored therein andsuitable for carrying out the steps of claim 9 .